The mass of sodium chloride : 3.5 g
Further explanation
Given
Reaction :
2.5g of sodium sulphate + 4.5g of barium chloride ⇒ 3.5g of barium sulphate + sodium chloride
Required
The mass of sodium chloride
Solution
Conservation of mass applies to a closed system, where the masses before and after the reaction are the same
From the reaction :
mass of reactants = 2.5 g + 4.5 g = 7.0 g
mass of products = 3.5 g + mass of sodium chloride
mass of reactants = mass of products
7.0 g = 3.5 g + mass of sodium chloride
mass of sodium chloride = 7 g - 3.5 g =3.5 g